Oxidation resistant lubricant compositions

ABSTRACT

Lubricants, especially lubricating oils and greases, containing an acyloxy-substituted diarylamine have improved oxidation resistance.

United States Patent Braid Oct. 23 1973 OXIDATION RESISTANT LUBRICANT [56] References Cited COMPOSITIONS UNITED STATES PATENTS [75] Inventor: Milton Braid, Westmont, NJ. 3,282,842 11/1966 Bonner 252/51.5 A

3,642,632 2/1972 Coburn [73] Assigneez zloYlnl Oil Corporation, New York, 3,660,290 5/1972 Schlobohm .1 252/5l.5 A

[22] Filed: Nov. 16, 1971 Primary Examiner-Werten F. W. Bellamy [21] A l N 199 372 Attorney-Andrew L. Gaboriault et al.

[57] ABSTRACT [52] F' 252/515 3 252/52 2 Lubricants, especially lubricating oils and greases, [51] C C g containing an acyloxy-substituted diarylamine have [58] Fied 0 Search 5 l5 .5 2,52/.52 R, improved oxidation resistance 10 Claims, No Drawings OXIDATION RESISTANT LUBRICANT COMPOSITIONS BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to novel compositions of matter useful in the preparation of lubricant compositions. In particular, the invention relates to lubricants to which have been added small amounts of an additive which will impart anti-oxidant properties thereto.

2. Discussion of the Prior Art Lubricating oils and greases are subject to oxidation deterioration at elevated temperatures or upon prolonged exposure to the elements. The deterioration is evidenced, in many instances, by an increase in acidity and in viscosity, and when such deterioration is severe enough, it can cause metal parts to corrode. Additionally severe oxidation leads to a loss of lubricating properties of the oil, and, in aggrevated cases, to complete breakdown of the lubricated part or of the entire machine. In combatting oxidation, many additives have been tried, but many of them are only marginally effective except at high concentrations, especially when the lubricants are subjected to drastic oxidizing conditions.

SUMMARY OF THE INVENTION DESCRIPTION OF SPECIFIC EMBODIMENTS The acyloxy-substituted diarylamines useful in the practice of this invention are those corresponding to the formula Ar-NH 0 11 wherein Ar is phenyl or naphthyl and R is an alkyl group having'from 1 to about 22 carbon atoms.

When used as antioxidants, the products of this invention are effective when they constitute from about 0.005 percent to about 15 percent by weight of the lubricant base. Preferably, such concentration is from about 0.01 percent to about percent by weight thereof, and more preferably from about 1.0 percent to about 5.0 percent by weight. The lubricants which may be improved by the addition thereto of the above-mentioned acyloxysubstituted diarylamine are mineral oils, both paraffinic and naphthenic, synthetic oils, and greases made therefrom. The synthetic oils include polyolefin fluids, polyglycols, polyacetals, the siloxanes and the like. Espe cially useful are those synthetic esters which are becoming more and more popular, particularly in aviation engines. These include esters made from polycarboxylic acids and monohydric alcohols, such as those obtained by reacting methanol, ethanol, propanol, butanol, neopentyl alcohol and the like with pimelic acid, azelaic acid, adipic acid and the like, or from polyhydric alcohols and monocarboxylic acids. Of these preferred members are those made from trimethylol alkanes, where alkane includes ethane, propane and butane, pentaerythritol, diand tripentaerythritol, or mixtures thereof and an aliphatic monocarboxylic acid containing from 1 to about 20 carbon atoms or a mixture of such acids. The most preferred are esters from the pentaerythritols and monocarboxylic acids having from 5 to 9 carbon atoms, or mixtures of these acids.

The following examples will serve to specifically illustrate the practice of the invention. It will be understood that they are illustrative only, and are not intended to limit the scope of the invention to a narrower range than described hereinabove.

EXAMPLE 1 4-Anilinophenyl Stearate To a solution of 46.3 g. of 4-anilinophenol in 400 ml of benzene at room temperature was added 11.5 g. of sodium metal chips, and the resulting mixture was stirred until all of the sodium had been consumed. To the resulting reaction mixture, 71 g. of stearoyl chloride was added during one hour at 25-42. Stirring at 2834 was then continued for 1.5 hr. more, and the reaction mixture was filtered and allowed to stand over night. Solids which precipitated were collected, crystallized from ethanol and then from benzene to afford 4- anilinophenyl stearate, tan crystals, melting at 78-7 9 C.

EXAMPLE 2 4-Anilinophenyl Pivalate To an ethanolic solution of sodium ethoxide prepared by the addition of l 1.5 g. of sodium metal to 175 ml of ethanol at 40-50 there was rapidly added 92.6 g. of 4-anilinophenol in 500 ml of benzene. Ethanol was removed by azeotropic distillation with benzene. A solution of 61 g. of pivaloyl chloride in ml of benzene was added to the reaction mixture at 68 during about 20 minutes while stirring. Stirring was continued while the reaction mixture cooled to room temperature and for an additional 3.5 hours. Treatment of the resulting reaction mixture with water precipitated 129.4 g. of crude 4-anilinophenyl pivalate which was crystallized from methanol to a tan solid melting at 7576 C.

EXAMPLE 3 4-( 2-Naphthylamino)phenyl Pivalate To a methanolic solution of sodium methoxide (from 6 g. of sodium metal and ml of methanol) 250 ml of benzene was added and methanol was distilled from the mixture. To the residue 47 g. p-2- naphthylaminophenol was added and then 30 g. of pivaloyl chloride was added during one hour at 60-70 C while stirring. The reaction mixture was kept stirring EXAMPLE 4 EXAMPLE 6 4-( l-Naphthylamino)phenyl Pivalate This compound was prepared by the procedure of Example 4 using the appropriate naphthylaminophenol.

EVALUATION OF PRODUCTS C Oxidation Test CHHRCO@ NH A 15 The compounds produced in accordance with this invention were blended into a synthetic ester oil V lubricant (made by reacting pentaerythritol with an equimolar mixture of C and C monocarboxylic acids) 4 (2 Naphthylamino)phenyl Laurate and tested m an ox1dat1on test in accordance with the To sodium p-Z-naphthylaminophenolate prepared by onowmg g h the reaction of 2.8 g. of sodium metal with 28 g. of p-2- Sampfe t fi z eagedhand naphthylaminophenol in 150 ml of diethyleneglycol dit e g 2: per ls P t mug methyl ether there was added while stirring at 100 C, a perm a ours reserllt t 6 test z 26.3 g. of lauroyl chloride during 0.75 hour. Stirring at f p E P i an z 100 C was continued for 6.5 hours after the addition c ange 2 (peicem l was completed. The reaction mixture was poured into aflge) mezsure i h an t i g neutral; ice-water and the solids which separated were collected 123mm ers ange) g re m g i and recrystallized from LProPano]. The the antioxidant effectllveness o arl1 ad ltivet. t s ou naphthylamino)phenyl laurate was thus obtained as a 30 be nofed that the P 5 g L meta engme or gray crystalline solid, melting point C. machine construction, an t ey a so prov1 e some catalysis for the oxidation of organic matenals. The re- EXAMPLE 5 sults are tabulated in the following table.

Weight percent Temp., Initial Initial AKV, Additive additive F. NN ANN KV, cs. percent 4 3.75 58 Example] 2 450 0.05 3.77 27.80 75 1 5.38 138 4 1.35 If 58 2 425 0.05 1.37 28.21 33 1 2.98 57 Example 2 4 5. 29 Example3 2} 450 0.11 5.14 30.85 84 1 7.47 110 Example 3 chromatographed 450 0 28.83 3 4. 04 73 Examp1e4 1. 5 450 0.05 5. 07 2s. 34 122 0. 75 6.18 100 Example 5 g} 450 0.10 1:3? 27. 0a

Examplefi f 450 0.05 g: 28.14 425 5.85 223 None T I claim: 0 1 l. A lubricant composition comprising a major (cH3)aCgo O amount of a lubricant and an amount sufficient to improve the antioxidant properties thereof of an acyloxy substituted diarylamine of the formula 3-Amhnophenyl Pivalate This compound was prepared using the method of o Example 4, except that the solvent was 1.2- Ar NH Q dimethoxyethane. After addition of the pivaloyl chloride at 60 C, the reaction mixture was refluxed at 85 for 3 hours. The product obtained was recrystallized from ethanol, and melted at 87-89 C.

wherein Ar is phenyl or naphthyl and R is an alkyl having from 1 to about 22 carbon atoms, the

5. The composition of claim 1 wherein the diarylamine is 4-anilinophenyl stearate.

6. The composition of claim 1 wherein the diarylamine is 4-anilinophenyl pivalate.

7. The composition of claim 1 wherein the diarylamine is 4-(2-naphthylamino)phenyl pivalate.

8. The composition of claim 1 wherein the diarylamine is 4-(2-naphthylamino)phenyl laurate.

9. The composition of claim 1 wherein the diarylamine is 3-anilinophenyl pivalate.

10. The composition of claim 1 wherein the diarylamine is 4-( l-naphthylamino)phenyl pivalate. 

2. The composition of claim 1 wherein the substituted diarylamine is present in said lubricant in an amount of from about 0.005 to about 15 percent by weight.
 3. The composition of claim 1 wherein the lubricant is a lubricating oil or grease.
 4. The composition of claim 3 wherein the lubricant is a lubricating oil.
 5. The composition of claim 1 wherein the diarylamine is 4-anilinophenyl stearate.
 6. The composition of claim 1 wherein the diarylamine is 4-anilinophenyl pivalate.
 7. The composition of claim 1 wherein the diarylamine is 4-(2-naphthylamino)phenyl pivalate.
 8. The composition of claim 1 wherein the diarylamine is 4-(2-naphthylamino)phenyl laurate.
 9. The composition of claim 1 wherein the diarylamine is 3-anilinophenyl pivalate.
 10. The composition of claim 1 wherein the diarylamine is 4-(1-naphthylamino)phenyl pivalate. 